Analytical reagents : standards and tests / compiled by Edmund White.

Date:
1911
Catalogue details

Licence: In copyright

Credit: Analytical reagents : standards and tests / compiled by Edmund White. Source: Wellcome Collection.

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    GOLD CHLORIDE. AuC1„HC1,4H20 Gold chloride, or aurochloric acid, the formula being some- times written HAuC14,4H20, occurs in yellow deliquescent crystalline masses, freely soluble in water and alcohol. The salt, according to the formula, contains 48 per cent, of metallic gold, but if free from impurities a slightly higher per- centage will be found, owing to the slight loss of hydrochloric acid and water which occurs in drying the crystals. Tests. Percentage of Gold: Dissolve 0 5 Gm. in 25 mils of water, render the solution distinctly alkaline with solution of potassium hydroxide, add1 5 mils of hydrogen peroxide solution (10 vols.), and heat to about 100° for an hour. Collect the precipitated gold, wash it with water acidulated with hydrochloric acid, dry, and cautiously ignite ; the residue should weigh not leas than 0'24 Gm. Foreign Metals: The filtrate from the foregoing test should not be affected by passing hydrogen sulphide through it, or by ammonium sulphide solution after supersaturation with am- monia. Sodium- Salt: Cautiously ignite 0'2 Gm. of the salt mixed with 0'5 Gm. oxalic acid in a porcelain crucible until all vola- tile matter has been driven off. Cool, and triturate the residue with 10 mils of water, filter, evaporate the filtrate to dryness. The residue should weigh less than 1 Mgm. Trade Varieties. Sodium aurochloride (NaAuCl4,2H,0), containing 49'5 per cent, of metallic gold, is sometimes sold as gold chloride, especially for photographic use. It is not so deliquescent as the foregoing 6alt, and is more easily obtained in detached yellow needle crystals. For analytical use the presence of the sodium is sometimes objectionable. Many varieties of so-called gold and sodium chloride are not the true compound, but contain only 20 to 30 per cent, metallic gold, and consist of gold chloride mixed with more or less sodium chloride. GLYCERIN. o3h5(0H)3. Viscid, clear, colourless, and odourless fluid, with a sweet taste. Miscible in all proportions with alcohol and water, but insoluble in chloroform, ether, benzene, or petroleum ether. Sp. gr., 1'25 to 126. Boiling-point, when anhydrous, 290° C. Readily attracts moisture when exposed to the air.